Automatic tension winch



July 23, 1935. w. c. DEAN AUTOMATIC TENSION wmcn Filed March 8, 1954 sSheets-Sheet 1 MOTOR I INVENTOR WALTER C. DEAN ATTOR EY July 23, 1935.w. c. DEAN 2,008,687

AUTOMATIC TENSION WINCH I Filed March 8, 1954 3 Sheets-Sheet 2 HOISTINGMANUAL CONTROL LOWERING MANUAL CONTROL AUTOMATIC CONTROL MOTOR STALLEDwnn TENSION ON LINE,- LOAD AT REST.

AUTOMATIC CONTROL PAYlNG OUT wm+ TENSlON ON LINE INVENTOR I WALTER CDEAN ATTOENEY y 3, 1935. w. c'. DEAN 2,008,687

AUTOMATIC TENSION WINCH Filed March 8, 1934 3 Sheets-Sheet 3 INVENTORWALTER C. DEAN BY ATTOR Ny Patented July 23, 1935 AUTOMATIC TENSIONWalter 0. Dean,

Application March 8,

24 Claims.

Chevy Chase, Md.

1934, Serial No. 714,657

(Granted under the act of March 3, 1888, amended April 30, 1928; 370 O.G. 757) This invention relates to mechanism for maintainingautomatically a predetermined tension in a line that is wound on a winchdrum to handle loads and more particularly adapted for use upon atilting platform, such as the deck of a ship, to hoist to said platformloads that are rising and falling due to wave action. Anotherapplication is for mooring winches where the lines from a ship to a dockhave to be, adjusted due to changes in tide or ships loading.

Among the objects of this invention are:

To provide means that will automatically take up slack in a line havingone end connected to a load and the other wound on a winch, or pay outthe line when the tension therein increases above a fixed maximum value;

To provide means for preventing the operation of the automatic mechanismwhen the load must be sustained by the line;

To provide a by-pass mechanism that will permit the automatic control oftension as above mentioned while the output of a variable deliveryhydraulic pump used to operate the winch continues in the samedirection.

In the drawings:

Fig. 1 is a schematic showing of the essential features of my invention;

Fig. 2 shows in detail the parts of my invention set for manual controlof the load;

Fig. 3 is similar to-Fig. 2 but discloses the mechanism set forautomatic control;

Fig. 4 shows diagrammatically the flow of the fluid in a hydraulicsystem embodying my invention when manual control is being used forhoist- 111g;

Fig. 5 shows the flow of the fluid during lowering under manual control;

Fig. 6 shows the path of the fluid when the control is automatic, theload being at rest, and the hydraulic motor is stalled with the tensionon the line;

Fig. 7 shows the movement of the fluid under automatic control whenpaying out the line;

ing platform, as in raising an airplane that is floating on the water tothe deck of a ship, but in all these mechanisms it is necessary that-thedirection of operation of the motive device be changed each time thatthe condition of the line changes from slack to load or vice versa. Thepresent invention permits the source of power to operate continuously inone direction, both when winding in the line and when paying it outunder automatic control. I v

In Fig. 1 the motor I2 is connected to drive a variable delivery pumpl3, commonly termed the A end, of a hydraulic speed gear, the fluid fromwhich is transmitted to and returned from the hydraulic motor, or B end,through pipes I5 and IS. The output of pump l3, both as to direction andquantity, is controlled by means of a spindle l1 having on it a toothedrack l8 meshed with a gear sector l9 carried by a hand lever 20 that ispivoted at 2|, the center of curvature of sector l9. Lever 20 is held inthe neutral, or no output position, of the pump controls by a detent 22engaged in a slot in looking quadrant 23, the detent being disengageablefrom the slot by the usual hand latch 24. The output' of thepump may be"made a maximum in either direction of rotation thereof by movement ofthe lever between stop 25 and removable pin 26, this range being usedfor handling loads, but when there is no load on the line and it isdesired to-increase considerably the speed of motor M for winding inslack, the pin 26 may be removed and the lever 24 be moved all the wayback to stop 21. Obviously, a pump having a rotary control spindleinstead of one having a sliding movement may be used.

A pinion 28 is meshed with gear 29 on which drum 30 upon which is woundline 3| that passes over a supporting member 32 to hoist the load 33.The gears 28 and 29 are overhauling, that is, when the driving effort ofhydraulic motor M exceeds the tension on line 3|, load 33 will behoisted, but when the tension on the line is greater than the efiort ofmotor I 4 the load 33 will fall and gears 29 and 28 will reverse thedirection of operation of motor I l and drive it as a'pump, at

which time the automatic by-pass valve 34 may pipe l6. For hoisting aload it is apparent that the surface beneath it would occur; also, ifthe valve 34 must be kept closed, otherwise the fluid line were payingout under automatic control and from pump |3 would be by-passed andwould not the device were shifted to manual control, the drive motor l4.A piston 35 mounted in cylinder resulting jerk on the line would eitherrupture 36 is connected to stem 31 of valve 34, the cylinthe line orseriously damage the load. The relader 36 being connectible to pipe l5through pipe 38 tive movement between the tilted platform and andthree-way valve 39, as shown in Fig. 2, there the load is zero at boththe lowest point of the roll being in pipe 38 a throttling valve 40. Itis eviand at the highest point of the roll but since dent that with thevalve 39 set as in Fig. 2, fluid the movements of the platform and ofthe load from pipe |5 will enter cylinder 36 and exert a are relativelyconverging at this latter point, force upon piston 35 proportional tothe pressure it would be undesirable to change to manual set up by thepump, which will hold the valve 34 control and being to hoist the loadat that time, on its seat. Cylinder 36 is connected to an ex- I havetherefore provided means for preventing pansion and air pressure chamber4| that may be the change from one type of control to the other openedto atmosphere by'removal of plug 42 for except at the lowest point inthe roll. If hoisting replenishing oil or for admitting air thereto. isbegun at that time the load and the platform Valve 34 is held againstits seat by a spring 43 diswill be in the most favorable relativepositions posed between acollar 44 on stem 31 and the inner and the loadcan be raised a suiiicient distance face of the end wall of a housing45. that it will'not contact the surface upon the next When themechanism is to be automatically downward roll of the platform. In Fig.8 the controlled, lever 46 is turned to the horizontal polever 46 isshown to be provided with a sector 52 sition shown in Fig. 3, whichrotates valve 39 to having in it two slots 53 and 54 that areengagedisconnect pipe 38 from pipe l5 and connects able by a pawl 55pivotally mounted at 56 and pipe 38 to an expansion tank 41 atatmospheric having an arm 51 disposed to be attracted by solepressure,under which conditions valve 34 is held noid 58 when the solenoid isenergized. A- penduagainst its seat by spring 43 only, the tension oflum 53, mounted to swing athwartship, has on it which is adjustable bychanging the position of a movable weight 60 and a contacting elementcollar 44 to permit valve 34 to be unseated by 6| adapted to close thecircuit through contactspressure in pipe |5 when the load on motor I4 62and 63 when the pendulum swings so that exceeds a predeterminedmagnitude. If, for exmember 6| bridges the gap between the two conample,it be desired to maintain a tension of tacts. By adjusting the tensionin control springs fifty pounds on the line 3|, the spring 43 will hold64 and 65 and the position of weight 66, the amvalve 34 on its seat atall pressures in pipe l5 up to plitude of swing of pendulum 59 can bemade that which is required to exert a tension of fifty such that thecircuit through contacts 62 and 63 pounds upon line 3| but when thepressure in will be closed at the lowest point in the roll of the pipel5 exceeds that value, valve 34 is unseated platform toward the load,which will energize and the liquid S y-p through e Valve 5 solenoid 58and thereby release pawl 55 from p p and b pump l3 and thus limits theengagement with sector 52 and leave lever 46 free driving force of motorl4 to that desired. As to be moved to change from automatic to manualvalve 34 is unseated the piston 35is moved back control or vice versa.in cylinder 36 which forces the fluid from the cylinder through P p 33to tank 47 a rate co sults is shown in Fig. 9. The wires 66 are sealedtrolled by the de ee of Op of Va ve 0 but into a down-bowed tubularmember 61 of electriiminediate unsenting Of the lv 34 iS made P 581-cally non-contacting material in which is a mass ble by passage of fluidinto the chamber 4|, which 68 of mercury, the member 61 being disposedto fluid is later forced by the air compressed in chamextendathwartship. The gap between the e 4| due to entry of the u d t that flsealed-in ends of wires 66 has the same function be to P s through p pe38 to tank 41. This airand position in the circuit as does that betweenpr n a i of h mber 4| resul in smoo her contacts 62 and 63 in Fig.8. Theone end of tube a better Operation of the Valve mechanism- 61 ispivotally supported at 69 and the other end e ap y of Va v 34 ispreferably twice the thereof is connected to an internally threadedOutput of p p l3 S c when he load s driving element 10 engaged with thethreads on screw II motor as a pump while pu p 3 continues to which hasa ball and socket connection with memfolce fill-id through P p the twoStreams bers 12 to permit tilting thereof but prevent refillid t p s tho Valve as Shown in moval of the screw therefrom. When the plat- Flg. 7.form tilts in the proper direction, mercury 68 will Co cted to the lev r6 at a distance from 1 envelop the ends of wires 66 and close thecircuit pivotal center thereof is a member 48 that is also through wires33 which energizes solenoid 53 Another device that accomplishesthe samereconnected to one arm of a bell crank lever 43 and remases tcQacting-lever 45 The degree Pivotally o t d at the elbow 0f the level,the of roll necessary to effect closing of the circuit -other arm oflever 49 being connected to the may be varied y turning screw 1 wherebyt movable P 26 to Withdraw the P m the path end of tube 61 that isconnected thereto will be of lever 20 and so permitthe moving of lever20 raised 1 quantity of mercury in ack o p 21 which gives P p themaxithe tube 61 may be varied by adding thereto or mum Output forWinding in the line at gh speed taking therefrom through the apertureclosed by under automatic control. Pin 26 is normally held member 13.- ithe P Of level by the action Spring Regardless of the position of theplatform with 50 which te ds t move the P p dly. respect to roll itwould be undesirable to change It is pp that there are certain times efrom manual control to automatic control while it would be u des ble tochange from manual hoisting a load. To prevent this, I have providedcontrol to automatic control or the reverse." For t means Sh n in Figs10 and 11 wherein the e p if-the Change m manual control to sheave 32over which line 3| passes is slidably automatic control were made when aload exceedmounted in the boom I4, the blocks 15 in which ing that forwhich valve 34 is set was partially the sheave is journalled beingnormally held in hoisted, a damaging impact of the load against theposition shown in Fig. 10 by spring 16 whereof the tension is adjustableby a screw I. Spaced contacts I8 are disposed to be bridged by anelement I9 and thus to close the circuit through the solenoid 58 when inthe position shown in Fig. 10. Tension on line 3| greater than apredetermined value will compress the spring I6 and move element I9 tobreak the circuit through contacts I8 which are connected by wires tothe wires 8| (Fig. 8). When switch 82 is opened the current from supplywires 83 must pass through wires 80 and hence if the circuit be brokenat contacts I8 the closing of the circuit at contacts 62 and 63 will notrelease pawl 55 to permit movement of lever 46. When it is desired tohave operation of lever 46 dependent on the roll of the platform only,switch 82 is closed which shuntsout the circuit that includes wires 8 I,80, etc.

With lever 20 in neutral position the delivery control of pump I3 isalso in the neutral position and consequently the pump executes nostroke and delivers no oil. The motor l4 and drum 30 are then at rest.Moving 20 to the right shifts control spindle l'I down into the pump andcauses the fluid from pump l3 to be delivered to motor I4 through pipe I6 and be returned through pipe l5 which lowers the load, the pump actingas a brake due to its fixed output. The circulation of the fluid duringthis operation is shown in Fig. 5. The reverse operation for hoistingthe load is schematically illustrated in Fig. 4, when lever 20 is movedto right and control spindle I1 is raised.

When automatic control lever 46 is rotated to the left, as seen in Fig.2, pin 26 is withdrawn which permits moving the lever 20 to its extremeposition at the left and opens the pump control to its maximum deliveryin the hoisting direction and causes motor I 4 to be driven to hoist thehook at a rate of say 300 feet per minute, but inasmuch as this rate ofdelivery of pump l3 would overload the motor I 2 if the line 3| werecarrying a load, this is never used except for taking up slack. When inautomatic control, if the load, as a hydroplane, drops into the troughof a wave or if the ship upon which the hoisting apparatus is mountedrolls away from the load, the tension on the line causes the winch todrive motor 14 as a pump and forces fluid back through pipe I5 whichunseats valve 34 and by-passes the fluid as shown in Fig. 7, the pump l3continuing its operation in the direction for hoisting meanwhile andtherefore as soon as the tension on the line is sufliciently decreasedvalve 34 is again seated and motor I4 is driven at high speed to wind inline 3| and to keep it taut. If the load remains stationary the motor I4is stalled with the predetermined tension exerted upon line 3| and thefluid from pump I3 is by-passed through valve 34 as indicated in Fig. 6.

Jerks on the line when going quickly from manual to automatic control orwhen all slack has been taken up and'the load is suddenly applied orwhen quickly changing from automatic to manual control are prevented bythe hydraulic slippage controlled by the cushioning action of the air inchamber H and the effect of throttling valve 40. A sudden jerk on line3|, during automatic operation, will unseat valve 34 and cause thebypassing of the fluid and if the additional load is but momentary theair pressure in chamber 4| will cause the fluid to flow back intocylinder 36 and reseat valve 34 but if continued the fluid will beforced through pipe 38 to tank 41 at a rate controlled by throttlingvalve 40.

The herein described invention may be manufactured and used by or forthe United States Government for governmental purposes, without thepayment of any royalty thereon.

I claim:

1. The combination with a variable delivery pump having a movablecontrol device and a hydraulic motor connected to said pump to be drivenby fluid therefrom, of a drum drivingly connected to said motor, a boom,a pulley mounted on said boom for limited sliding movement, a cable oversaid pulley connected to said drum to be wound thereon, resilient meansacting on said pulley to move it in the direction opposed to the forceexerted thereon by a load on said cable, a pair of electric contacts onsaid boom, a member carried by the pulley mounting to close the circuitthrough said contacts when the load on the cable is insuflicient toovercome said resilient means, means between said motor and. said pumpto control automatically the tension in said cable, means to render saidautomatic means operative or inoperative, means to lock said lastmentioned means, and electric means connected in circuit with saidcontacts to release said locking means when the circuit is closedthrough said contacts.

2. The combination with a variable delivery pump having a movablecontrol device and a hydraulic motor connected to said pump to be drivenby fluid therefrom, of a drum drivingly ,connected to said motor, aboom, a pulley mounted on said boom for limited sliding movement, acable over said pulley connected to said drum to be wound thereon,resilient means acting on said pulley to move it in the directionopposed to the force exerted thereon by a load on said cable, a pair ofelectric contacts on said boom, a member carried by the pulley mountingto close the circuit through said contacts when the. load on the cableis insufficient to overcome said resilient means, means between saidmember and said pump to control automatically the tension in said cable,means to render said automatic means operative or inoperative, means tolock said last mentioned means, manually movable means to actuate saidcontrol device, means to limit the movement of said manually movablemeans in one direction, and means operatively connected to the thirdmentioned means to render said limiting means inoperative simultaneouslywith rendering said automatic means operative.

3. The combination with a variable delivery pump having a movablecontrol device and a hydraulic motor connected to said pump to be drivenby fluid therefrom, of a drum drivingly connected to said motor, a cableconnected to said drum to be windable thereon, means to controlautomatically the tension in said cable, means to render said automaticmeans operative or inoperative, means to manipulate the controls of saidpump, means to limit the operation of the last mentioned means in onedirection, and means connected to the second mentioned means to rendersaid limiting means inoperative simultaneously with placing saidautomatic means in the operative condition.

4. The combination with a variable delivery pump having a movablecontrol device and a hydraulic motor connected to said pump to be drivenby fluid therefrom, of a drum drivingly connected to said motor, a cableconnected to said drum to be windable thereon, means adjustable tofunction automatically to by-pass fluid from said pump around said motorwhen the load on said cable exceeds a predetermined magnitude, means torenderthe aforesaid means operative or inoperative, means to limit theoperation of said control device in one direction, and means ing .endand disposed to be unseated by pressure connected to said secondmentioned means to render said limiting means inoperative, simul--taneously with placing said automatic means in the operative condition.

5. The combination with a variable delivery pump having a movablecontrol device and a hydraulic motor connected to said pump to be drivenby fluid therefrom, of a drum drivingly connected to said motor, a cablecomiected to said drum to be windable thereon, automatically actingmeans to by-pass fluid from'said pump around said motor when the load onsaid cable exceeds a predetermined magnitude, means to render theaforesaid means operative or inoperative, means to limit the operationof said control device in one direction, and means connected to saidsecond mentioned means to render said limiting means inoperativesimultaneously with placing said automatic means in the operativecondition.

6. The combination with a hydraulic speed gear'having a driving end, adriven end connected thereto by two pipes and means to control the fluiddelivery of said driving end, of a valve operatively connected to bothof said pipes between said ends, said valve having a capacity ofsubstantially double the output capacity of the driving end and disposedto be unseated by pressure from one pipe, adjustable loading means tourge said valve against its seat, a piston operatively connected to thevalve to hold the valve seated, a cylinder in which said piston ismounted, means to connect said cylinder either to said one pipe or toatmospheric pressure, a throttling valve in said connecting means, andair cushion means connected to receive fluid from said cylinder uponmovement of the piston 'into the cylinder.

7. The combination with a hydraulic speed gear having a driving end, adriven end connected thereto by two pipes and means to control the fluiddelivery of said driving end, of a valve operatively connected to bothof said pipes between said ends, said valve having a capacity ofsubstantially double the output capacity of the driving end and disposed,to be unseated by pressure from one pipe, adjustable loading means tourge said valve against its seat, a piston operatively connected to thevalve to hold the valve seated, a cylinder in which said piston ismounted, means to connect said cylinder either to said one pipe or toatmospheric pressure, and a throttling valve in said connecting means.

8. The combination with a hydraulic speed gear having a driving end,'adriven end connected thereto by two pipes and means to control the fluiddelivery of said driving end, of a valve operatively connected to bothof said pipes between said ends, said valve having a capacity of sub.-stantially double the output capacity of the driving end and disposed tobe unseated by pressure from one pipe, adjustable loading means to urgesaid valve against itsseat, a piston operatively bonnected to the valveto hold the valve seated,

a cylinder in which said piston is mounted, and

means to connect said cylinder either to said one pipe or to atmosphericpressure.

9. The combination with a hydraulic speed gear having a driving end, adriven end connected thereto by two pipes and means to control the fluiddelivery of said driving end, of a valve operatively connected to bothof said pipes between said ends, said valveehaving a capacity ofsubstantially double the output capacity of the drivfrom one pipe,adjustable loading means to urge saidvalve against its seat, and meansselectively settable either to apply pressure in said one pipe to holdthe valve on its seat or to place said valve solely under the control ofthe loading means.

10. The combination with a hydraulic speed gear having a driving end, adriven end connected thereto by two pipes and means to control the fluiddelivery of said driving end, of a valve operatively connected to bothof said pipes between said ends, said valve having a capacity greaterthan the output capacity of the driving end and disposed to be unseatedby pressure Irom one pipe, adjustable loading means to urge said valveagainst its seat, a piston operatively connected to the valve to holdthe valve seated, a

the operation of said control means operatively connected to the lastmentioned means to render said limiting means inoperative when said lastmentioned means is in position to connect said cylinder to atmosphericpressure.

11. The combination with a hydraulic variable speed gear having adriving end, a driven end connected thereto by two pipes and means tocontrol the fluid delivery of said driving end, and a valve operativelyconnected to both said pipes between said ends, said valve beingdisposed to be unseated by pressure from one pipe, and adjustable loadmeans to urge said valve against its seat, means selectively settableeither to apply pressure in said one pipe to hold the valve on its seator to place said valve solely under the control of the loading means,and means to limit theoperation of said control means operativelyconnected to the last mentioned means to render the limiting meansinoperative when said valve is controlled solely by the loading means.

' 12. The combination with a hydraulic variable speed gear having adriving end, a driven end connected thereto by two pipes and means tocontrol the fluid delivery of the driving end, of means to by-pass fluidfrom the driving end around the driven end in response to a load on saiddriven end in excess of a predetermined magnitude and means actuatableby the pressure set up by the driving end to prevent operation of saidby-pass means.

13. The combination with a hydraulic variable speed gear having adriving end and a driven end and means to control the delivery of saiddrivin end, of a drum drivingly connected to said driven end, a cableconnected to said drum to be wound thereon, means to limit the operationof said control means in the direction to wind the cable on said drum,automatic means to cause said driven end to wind said cable on the drumwhen the load on the cable is less than a predetermined value or permitthe load to unwind the cable from the drum when the said load is greaterthan the said value, means to render said automatic means operative orinoperative at will, and means connected to said last mentioned meansand to said limiting means to render said limiting means inoperativewhen said automatic means is operative.

14. A winch mechanism adapted for use on a tilting platform, comprisingthe combination with a hydraulic variable speed gear having a drivingend and a driven end and means to control the delivery from said drivingend, of a drum. re-

versible driving means between said drum and said driven end, a cableconnected to said drum to 'be wound thereon, automatic by-pass means topass fluid from said driving end around. said driven end when the loadon said drum exceeds a predetermined magnitude, means to render saidby-pass means operative or inoperative, means to lock the last mentionedmeans, electric means to release the said lock, means actuated bymovement of the mechanism with the platform to close at one point anelectric circuit through said electric means at the moment of greatesttiltdn the direction o'fextent of said cable, other means to close saidcircuit at a second point through said electric means when the load onsaid cable is less than a predetermined value, means to limit themovement of said control means in one direction, and means connected tosaid limiting means and to the means for rendering said by-pass meansoperative or inoperative to render said limiting means ineffective whensaid by-pass means is operative.

15. A winch mechanism adapted for use on a tilting platform, comprisingthe combination with a hydraulic variable speed gear having a drivingend and a driven end and means to control the delivery from said drivingend, of a drum, reversible driving means between said drum and saiddriven end, a cable connected to said drum to be wound thereon,automatic by-pass means i to pass fluid from said driving end aroundsaid driven end when the load on said drum exceeds a predeterminedmagnitude, means to render said by-pass means operative or inoperative,means to lock the last mentioned means, electric means to .release saidlock, means actuated by movement of the mechanism with the platform toclose at one point an electric circuit through said electric means atthe moment of greatest tilt in the direction of extent of said cable,and other means to close said circuit at a second point through saidelectric means when the load on said cable is less than a predeterminedvalue.

16. A winch mechanism for use on a tilting platform, comprising thecombination with a source of power, of a drum driven by said source, acable windable on said drum, automatic means to apply the power to windsaid cable on said drum when the load is of less than a predeterminedmagnitude or to permit said load to unwind said cable when the load isgreater than said magnitude, a device to render said automatic meansoperative or inoperative, means to lock said device in the inoperativeposition of the automatic means, electric means to release said lockingmeans, a circuit to conduct current to said electric means, includingspaced contact members, a pendulum, a bridging member carried by saidpendulum to close the circuit through said contacts when caused bytilting of the platform to swing against them, and means acting on saidpendulum to hold said bridging member normally away from said contacts.

17. A winch mechanism for use on a tilting platform, comprising thecombination with a source of power, of a drum driven by said source,

' a cable windable on said drum, automatic means to apply the power towind said cable on said drum when the load is of less than apredetermined magnitude or to permit said load to unwind said cable whenthe load is greater than said magnitude, a device to render saidautomatic means operative or inoperative, means to lock said device inthe inoperative position of the automatic means, electric means torelease said locking means, a circuit to conduct current to saidelectric means including spaced contact members, a down-bowed tubularelement of insulating material into one end of which said contactsproject, and a globule of electrically conducting liquid in said elementto close the circuit through said contacts when movedby tilting of theplatform to envelope both said contacts.

18. A winch mechanism for use on a tilting platform, comprising thecombination with a source of power, of a drum driven by said source, acable windable on said drum, automatic means to apply the power to windsaid cable on said drum when the load is less than a predeterminedmagnitude or to permit said load to unwind said cable when the load isgreater than said magnitude, a device to render said automatic meansoperative or inoperative, means to lock said device in the inoperativeposition of the automatic means, electric means to release said lockingmeans, a circuit to conduct current to said electric means includingspaced contact members, and means actuatable by tilting of the platformto close the circuit through said contacts.

19. A winch mechanism for use on a tilting platform, comprising thecombination with a source of power, of a drum driven by said source, acable windable on said drum, automatic means to apply the power to windsaid cable on said drum whenthe load is less than a predeterminedmagnitude or to permit said load to unwind said cable when the load isgreater than said magnitude, a device to render said automatic meansoperative or inoperative, means to lock said device in the inoperativeposition of the automatic means, electric means to release said lockingmeans, a circuit to conduct current to said electric means includingspaced contact members at each of two points in said circuit, meansactuatable by tilting of the platform to close the circuit through thecontacts at one of said points and other means responsive to the load onsaid cable to close the circuit at the other of said points when saidload is less than a predetermined magnitude.

20. The combination with a driving device and a driven device, of a drumhaving a reversible driving connection with said driven device,a cablewindable on said drum, automatic means to cause said cable to be woundon said drum or paid out in response to a decrease of load on the cablebelow or increase of the load above a predetermined value, respectively,the direction of operation of the driving device remaining unchanged,means to render said automatic means inoperative and cause said drivingdevice positively to control said drum, means responsive to the positionof the mechanism with respect to the horizontal to prevent changing frompositive control to automatic control except in a predetermined positionwith respect to the horizontal, and means responsive to the load on saidcable to prevent the said change when the load exceeds a predeterminedmagnitude.

21. The combination with a driving device and a driven device, of adrumhaving a reversible driving connection with said driven device, a cablewindable on said drum, automatic means to cause said cable to be woundon said drum .or paid out in response to a decrease of load on the cablebelow or increase of the load above a predetermined value, respectively,means to render said automatic means inoperative and cause said drivingdevice positively to control said drum, means responsive to the positionof the mechanism with respect to the horizontal to prevent changing frompositive control to automatic control except in a predetermined positionwith respect to the horizontal, and means responsive to the load on saidcable to prevent said change when the load exceeds a predeterminedmagnitude.

22. The combination with a driving device and a driven device, of a drumhaving a reversible driving connection with said driven device, a cablewindable on said drum, automatic means to cause said cable to be woundon said drum or paid out in response to a decrease of the load on thecable below or increase above a predetermined value,,

driving direction with said driven device, 'a cable windable on saiddrum, automatic means to cause said cable to be wound on said drum orpaid out in response to decrease of the load on said cable below orincrease above a predetermined value, respectively, means to render saidautomatic means inoperative and cause said driving device positively tocontrol said drum, and means responsive to the load on said cable toprevent the said change when the said load exceeds a predeterminedmagnitude.

24. The combination with a hydraulic variable speed gear having adriving end and a driven end connected thereto by two pipes and means tocontrol the fluid delivery of the driving end, of a valve to by-passfluid from the driving end around the driven end in response to a loadon said driven end in excess of a predetermined magnitude, and

' means selectively operable by pressure from said driving end tomaintain said valve against its seat. 20

WALTER C. -DEAN.

